The woe of leks

Rare Gunnison sage-grouse populations sag because of their own mating behavior

Gunnison sage-grouse looks a bit like this... Pity the poor Gunnison sage-grouse Centrocercus minimus. Teetering on the edge of extinction, the recently described bird, found only in southwestern Colorado and southeastern Utah, suffers from the loss of almost three quarters of its brood, according to a two-year study published recently in Biological Conservation. Using a combination of painstaking field observation and computer simulation, University of Nebraska-Lincoln biologist Robert Gibson and colleagues also found that the sage-grouse is a victim of its own lek-based mating system: the handful of males that do almost all of the mating bring the effective population size dangerously low to the threshold needed to fend off the worst effects of inbreeding. Because only a few males mate, and only a few females’ chicks subsequently survive, it’s as though the population is much smaller than it really is. There’s rare, and then there’s rare. Source: Stiver JR, Apa AD, Remington TE & Gibson RM (2008) Polygyny and female breeding failure reduce effective population size in the lekking Gunnison sage-grouse. Biological Conservation DOI: 10.1016/j.biocon.2007.10.018